In the printing and graphic arts, efforts are constantly made to develop new and improved inks for printing on a variety of surfaces. In particular demand are those fluid inks which can be printed or laminated on various packaging materials, such as polypropylene, polyester, and nylon films. These inks must also possess a number of qualities in order to be employed commercially, such as good adhesion to the films and high lamination bond strengths. It is thus highly desirable to develop inexpensive ink formulations with the characteristics necessary for use as a laminating ink.
The primary ingredients of fluid ink compositions are pigment, resin vehicle, and solvent. In attempts to develop superior fluid ink compositions, efforts have been directed at developing an improved resin vehicle which will impart the characteristics necessary for an ink to be used successfully in film lamination. During these attempts to develop new fluid ink resins, amido-amine compositions known to be useful as epoxy curing agents, as disclosed in U.S. Pat. No. 3,417,140 (McWhorter et al), were investigated. These amido-amine compositions were prepared by reacting a mixture of a fatty amine and polyamine with an unsaturated carbonylic compound through a Michael addition, followed by the condensation of an amine group with the carbonylic group. However, in tests producing these compounds in accordance with the teaching of the McWhorter et al patent, it was found that the products thus obtained were either of undesirably low molecular weight or were crosslinked. In either case, these compositions are unsuitable as laminating ink resins. It was desired, therefore, to find other resins which could be used successfully in fluid printing inks, and which would be particularly suitable for use in laminating fluid inks.